UNITED NATIONS — Vice President George Bush today called the accidental U.S. destruction of an Iranian airliner carrying 290 people a "terrible human tragedy" but told the U.N. Security Council that Iran shares in the responsibility.

Presenting the U.S. case in the Security Council's debate on the downing of Iran Air Flight 655, Bush defended the U.S. naval presence in the Persian Gulf as "our legal right." Iran, which asked for a council condemnation of the U.S. action, was represented by its foreign minister, Ali Akbar Velayati.

Bush said Iran "allowed a civilian aircraft loaded with passengers to proceed on a path over a warship engaged in battle. That was irresponsible and a tragic error."

In an angry 1 1/2-hour speech before Bush's 25-minute address, Velayati said the United States had committed a "barbaric crime" and denied U.S. claims that the Navy warned the jetliner before the attack.

Velayati charged that the attack had been premeditated.

'Most Inhuman Attack'

"This was the most inhuman military attack in the history of civil aviation," he said, accusing the United States of "arrogance, indifference and a campaign of lies . . . to justify this barbaric crime at any cost. . . .

"This was a premeditated act of aggression against the integrity of Tehran . . . a massacre," he said.

Bush said he would not "dignify with a response the charge that we deliberately destroyed Iran Air 655."

And he said Velayati "knows better."

Bush called the Persian Gulf a "region of vital importance to the United States and the economy of the world." He said the U.S. presence in the gulf is intended to help ensure the flow of oil and protect neutral commerce. "This is our legal right," he said.

Bush, as he has done repeatedly over the last 10 days, defended the captain of the warship Vincennes. "One thing is clear," he said. "The USS Vincennes acted in self-defense" in firing two missiles at the jetliner, which it had deduced was a far smaller Iranian F-14 fighter closing in on the cruiser.

Bush called on Iran to immediately divert civilian air traffic away from areas of "active hostilities" and to join with Iraq in accepting an immediate cease-fire in the war that has raged since 1980.

"The victims of Iran Air 655 are only the most recent casualties of a brutal and senseless war that has brought immense pain and suffering to the people of both sides," Bush said.

Bush said he came to the United Nations, where he served as ambassador from 1971 to 1973, at the request of President Reagan, "because of the importance of the issues at stake."

High-Visibility Role

Bush said it was "not just the terrible human tragedy of Iran Air 655 but the continuing conflict between Iran and Iraq" that brought him to speak.

His appearance gave the certain Republican presidential nominee high visibility at a time when Democrats are preparing to nominate Michael S. Dukakis as their presidential candidate.

Presidential spokesman Marlin Fitzwater denied that Reagan's selection of Bush was made for political reasons.

The speech is Bush's first speech to the Security Council since he was ambassador under President Richard M. Nixon. U.N. officials said no U.S. vice president had addressed the council in recent memory.

In the days after the shooting down of the airliner, Bush was outspoken in his defense of the captain of the Vincennes, Will Rogers III, calling the episode in the Persian Gulf "just an unhappy incident" and telling audiences repeatedly, "Life goes on."